Current methods and apparatus for mixing a plurality of materials together in the medical field, e.g., poly(methyl-methacrylate) bone cement comprising a powdered material with a liquid monomer to be used as a bone filling material, often yield unsatisfactory results.
Typically, in a surgical setting, the instruments employed for this purpose are a small bowl for receiving the components and a stick (such as a common tongue depressor) for mixing the components in the bowl. If a powdered material is employed, it is usually poured directly from its container into the bowl. Consequently, the process is often messy due to spillage of the powdered material. Where one of the components is a liquid monomer, the process can involve the release of noxious fumes released by the liquid monomer.
After the components are mixed, as in the case of a bone filling material, further problems are encountered. When the bone filling material is to be dispensed into a cavity in bone, the common practice is to first transfer the material into a syringe and then to transfer the material from the syringe into another instrument for delivery to the cavity. The syringe is loaded by either vacuuming up the material by withdrawing the fully engaged plunger through the syringe body, or by removing the syringe plunger and pouring the material into the back of the syringe and reinserting the plunger. This is a difficult and messy procedure, and there is often material loss from each step of the transfer (from spillage and/or residual material left in the dispensing bowl and/or lumens, etc.)
One example of a bone cement mixing and delivery system that provides some containment is shown in U.S. Pat. No. 5,193,907 to Faccioli et al. Faccioli discloses an apparatus for mixing and delivering bone cement formed from liquid and powder components. The apparatus comprises a cylindrical body and a plunger slidable within the body. A powder chamber stores the powder component between the plunger and a distal end of the body. A glass ampoule stores the liquid component inside the plunger. To mix the components, a user presses a plug in the plunger's proximal end to urge a tip of the glass ampoule against a cammed surface (or against a piercing member) to release the liquid component. The liquid component then passes through channels defined in the plunger's head to the powder chamber. The liquid and powder are mixed by shaking the body to form the bone cement mixture. After mixing, the plunger is pressed to discharge the bone cement mixture out of an exit port in the body and through a flexible conduit to a target site.
Another example of a bone cement mixing and delivery system is shown in U.S. Patent Publication No. 20100110820 to Coffeen et al. Coffeen et al discloses a battery-powered apparatus for mixing and delivering bone cement that utilizes the same motor to actuate both the mixing paddle and the transfer mechanism to minimize weight, cost, and waste, in a single use (disposable) system. According to Coffeen, the system and method of the present invention reduce user interaction compared to prior art devices and increases the readiness in which an operator can prepare a batch of bone cement for surgical purposes.
These prior art systems seek to reduce system set-up times, conserve a user's energy and/or reduce exposure of the user to the bone cement components. However, there is still a need in the art for bone cement mixing and delivery systems that have few components and are capable of mixing materials while containing the fumes and to easily and cleanly transfer and/or dispense the contents into other instruments.